|HERGERT, GARY - University Of Nebraska|
|Jabro, Jalal "jay"|
|NIELSEN, REX - University Of Nebraska|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2016
Publication Date: 2/28/2017
Publication URL: http://handle.nal.usda.gov/10113/6472162
Citation: Mikha, M.M., Hergert, G.W., Benjamin, J.G., Jabro, J.D., Nielsen, R.A. 2017. Soil organic carbon and nitrogen in long-term manure management system. Soil Science Society of America Journal. 81:153-165.
Interpretive Summary: The dynamics of soil organic carbon (SOC) as impacted by various agricultural practices is challenging and not well understood. Therefore, long-term studies are carried out to enhance our knowledge with continual changes in soil quality parameters that are more difficult to evaluate with short-term experiments. The objectives of this study were to evaluate SOC, soil total N (STN), particulate organic matter (POM) and its associated C (POM-C), and mineral-associated organic matter C (MAOM-C) after 70 years of moldboard plowing, beef manure (M) amendments, commercial fertilizer (F) additions, and the combination of F+M. Soil C and N were further presented on a fixed depth (FD) and on an equivalent soil mass (ESM) basis to evaluate the differences between two computation’s approaches on soil C and N storage. With both approaches, soil C and N were higher for the top 0-30 cm of the soil than 30-60 cm depth by 2.3 fold and higher than 69-90 cm layer by 3 fold. The amount of soil POM increased with the combination of F+M by approximately 52% with 180+M and by 36% with 90+M treatments compared with only F treatment. The amount of POM-C in proportion to SOC was 43% greater in the surface layer than in the subsurface layer. On the other hand, the proportion of MAOM-C to SOC was 7% greater in the lower 15-30 cm compared with the top 0-15 cm. Overall, the results indicate that long-term additions of manure-based amendments enhanced SOC and its distribution by depth between soil carbon pools.
Technical Abstract: Long-term studies are extremely beneficial to understand and evaluate changes in soil quality and sustainability of specific management practices. The objectives of this study were to evaluate the effects of 70 yr of moldboard plowing with manure (M) and commercial fertilizer (F) additions on soil organic C (SOC), soil total N (STN), particulate organic matter (POM) and its associated C (POM-C), and mineral-associated organic matter C (MAOM-C). The Knorr-Holden plots were initiated in 1912 on a Tripp sandy loam (coarse-silty, mixed, superactive, mesic Aridic Haplustolls) with furrow irrigated, continuous-corn (Zea mays L.) production. In 2011, soil samples were collected from the 0-5, 5-10, 10-15, 15-30, 30-60, and 60-90 cm depths. Treatments were evaluated for the form of stability and distribution of SOC as POM, POM-C, and MAOM-C. On a fixed depth basis (FD), SOC and STN in the 0-30 cm layer increased by 2.3 fold compared with 30-60 cm layer and by 3 fold compared with 60-90 cm layer. Similar differences in SOC and STN were observed when calculated on an equivalent mass (ESM) basis. Compared with 90 and 180 kg N ha-1, application of manure with fertilizer (F+ M) increased POM content in 0-30 cm depth by 36% and 52% with 90+M and 180+M respectively. In the 0-15 cm soil depth, the relative POM-C to SOC content was 43% greater than in 15-30 cm soil depth. In the 15-30 cm depth, MAOM-C was 7% higher than the surface 0-15 cm depth. The MAOM-C represented 69% of SOC content associated with different treatments Positive and significant correlations were found among SOC, POM-C, and MAOM-C. Overall, manure-based amendments, with or without F, enhanced SOC and its distribution by depth between soil C pools investigated.